Vanguard

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With all the world watching on March 17, 1958, NRL's Vanguard Test Vehicle-4 rocketed skyward from Cape Canaveral, Florida, and 10 minutes later it was confirmed that the grapefruit-sized satellite had separated from its launch vehicle and was in earth orbit.

This space feat culminated the efforts of America's first official space satellite program begun on September 9, 1955.

As part of the scientific program for the International Geophysical Year (1957-58) the NRL was officially delegated the responsibility of placing an artificial satellite with a scientific experiment into orbit around the earth. Designated Project Vanguard, the program was placed under Navy management and DoD monitorship.

NRL's proposal to conduct Project Vanguard was based on experience gained from extensive use of German V-2 and Viking rockets to probe the earth's upper atmosphere.

Objectives of Project Vanguard:

develop and procure a satellite-launching vehicle;
place at least one satellite in orbit around the earth during IGY;
accomplish one scientific experiment; and
track Vanguard's flight to demonstrate the satellite actually attained orbit.

In conjunction with the Vanguard launch, NRL scientists laid out a worldwide tracking system called Minitrack. Laboratory scientists later used many of the principles embodied in this system to develop a Space Surveillance System which can detect unannounced, radio-silent satellites passing over the U.S.

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In the 35 years following Vanguard's launch the 3-pound satellite made more than 147,750 revolutions of the earth and travelled over four billion nautical miles, the distance from earth to beyond the planet Neptune and back. In that time it has provided a wealth of information on the size and shape of the earth, and set a number of space records as well.

The successes of Vanguard I set the pattern for a multitude of other space ventures in this country and abroad. Vanguard also served as a springboard for NRL scientists to launch several series of space probes to study various aspects of radiation phenomena.

Vanguard I introduced much of the technology that has been applied in other U.S. satellite programs. For example, it proved that solar cells could be used for several years to power radio transmitters. Vanguard's solar cells operated for about seven years, while conventional batteries used to power another onboard transmitter lasted only 20 days.

Now the oldest man-made satellite in orbit, Vanguard I has been 100 percent successful in meeting its scientific objectives.

First orbiting package to be powered by solar energy.
Returned a wealth of information on air density, temperature ranges and micrometeorite impact.
Maintained an orbit so stable that cartographers were able to more accurately redrawn maps of islands in the Pacific Ocean.
Revealed that the earth is slightly pear-shaped rather than round.

Although Vanguard's solar-powered "voice" became silent in 1964, it continues to serve the scientific community. Ground-based tracking of the satellite provides data concerning the effects of the sun, moon, and atmosphere on satellite orbits.

Fifteen years after its launch, Vanguard was in an orbit with an apogee height of 2,121 nautical miles above the earth's surface, and a perigee of about 353.6 nautical miles. The orbit period was approximately 133.8 minutes.
By mid-1995 Vanguard was in an orbit with an apogee height of 2,087 nautical miles above the earth's surface, a perigee of 351 nautical miles, and an orbit period of 133.1 minutes.

Drag has brought down the apogee and perigee, resulting in a decrease in period. Vanguard I's orbital history illustrates the phenomenom of drag bringing down apogee much more than perigee.